The present invention refers to sealing devices of the labyrinth type, i.e. co-operating sealing elements are not abutting each other but there is a gap therebetween. In particular, the invention refers to a sealing device for sealing a gap between a first member and a second member, the first member being rotatable in relation to the second member about an axis of rotation, and one of the two members forming a cavity within itself, in which the other of the two members extends axially and thereby forms said gap between the two members, the sealing device comprising a first sealing element, having a first attachment member arranged to be fixedly provided on the first member and extend around the axis of rotation and from the first member extend towards the second member, and a second sealing element, having a second attachment member arranged to be fixedly provided on the second member and extend around the axis of rotation and from the second member extend towards the first member closely adjacent to the first sealing element without direct contact with the latter and with the first member.
In many technical constructions and applications, it is a problem to provide a sealing which is sufficiently good due to the clearances which have to exist between two members being rotatable relative to each other. One example of such an application is centrifugal separators having a support and a driving shaft extending through a stationary wall into the space in which the centrifugal separator rotates. Due to the high number of revolutions of the driving shaft and its frequently large radial movements, lip sealings or other abutting machine sealings may not be used, but contact free sealing devices such as labyrinth sealings are often the only alternative. In addition, since there may be a pressure difference between said space and the surroundings, it is very difficult to avoid a certain flow through the labyrinth sealing. This means that unwanted particles and liquids will be transported by the flow.
GB-A-2 157 373 discloses a conventional labyrinth sealing for sealing a passage for a rotating shaft. The labyrinth sealing comprises a first sealing element which is intended to be provided at the shaft and which comprises a number of flanges extending radially outwardly, and a second sealing element which comprises a number of flanges extending radially inwardly in the spaces between the flanges of the first sealing element.
DE-A-3 908 372 discloses a similar conventional labyrinth sealing comprising rotating and stationary, respectively, flanges provided adjacent to each other and extending in radial planes.
U.S. Pat. No. 5,085,443 discloses a floating labyrinth sealing for a centrifugal separator. The sealing comprises a number of teeth extending in the peripheral direction and axially and radially, respectively, towards a rotating shaft and enclosing a number of chambers. The intermediate chamber is connected to a channel for the supply of nitrogen gas.
GB-A-2 128 693 discloses another type of labyrinth sealing which is intended for sealing a rotating shaft and which comprises chambers delimited in the peripheral direction.
DE-A-4 313 805 discloses a sealing device for a turbine and in particular for the turbine shaft passage through the turbine housing. The sealing device comprises a number of chambers which are provided adjacent to each other in the passage and which enclose and are open towards the turbine shaft. A suction device is arranged for sucking away the gas or steam entering the chambers.
U.S. Pat. No. 5,026,075 discloses a radial labyrinth sealing for a turbine device. The sealing comprises radial flanges provided at the turbine housing and radial flanges provided at the turbine rotor and extending between the flanges of the turbine housing. Furthermore, this document discloses the arrangement that the flanges of the rotor are provided with projecting sealing portions, the outer ends of which are located very close to the turbine part, making the sealing disclosed inappropriate when relatively radial movements occur between the rotating and stationary parts.